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<title>ALE User Manual: Rendering Chains</title>
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<a href="http://auricle.dyndns.org/ALE/">
<big>ALE</big>
<br>
Image Processing Software
<br>
<br>
<small>Deblurring, Anti-aliasing, and Superresolution.</small></a>
<br><br>
<big>
Local Operation
</big>
<hr>
localhost<br>
2684415918<br>
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<p><b>[ <a href="../">Up</a> ]</b></p>
<h1>ALE Rendering Chains</h1>
<p>The ALE incremental renderer is configured using rendering chains. Rendering chains are
constructed hierarchically from: invariants, SSFEs (scaled sampling filters
with exclusion), SSFs (scaled sampling filters), and sampling filters. Each of
these components is described in a section below. Defaults are outlined in the
final section.
<h2>Chains</h2>
<p>The chain is the top level of the rendering chain hierarchy, and is composed of a
sequence of invariants. Syntactically, a chain is specified as a number of
invariants separated by commas:
<blockquote>
<code>invariant<sub>1</sub>,invariant<sub>2</sub>,invariant<sub>3</sub>,...,invariant<sub>n</sub></code>
</blockquote>
<p>Each rendered pixel is assigned a value at the first invariant whose weight
exceeds the weight threshold, or otherwise at the last invariant in the sequence.
<h3>Chain Options</h3>
<pre>
--wt &lt;w&gt; Set weight threshold for defined pixels [default is 0.8 in v0.8.0; 0.1 in v0.8.1 and later]
--dchain &lt;g&gt; Use chain &lt;g&gt; to render the default output.
--ochain &lt;g&gt; &lt;o&gt; Use chain &lt;g&gt; to render output file &lt;o&gt;.
--achain &lt;g&gt; Use chain &lt;g&gt; to render the alignment reference image.
--3d-chain &lt;g> Use chain <g> by default to render 3d output. [0.8.4 and later]
</pre>
<h3>Chain Examples</h3>
<pre>
triangle:2 ALE 0.6.0 merging (roughly)
fine:box:1 Drizzling (roughly)
fine:sinc*lanc:8 High-frequency preservation
last:nex:sinc*lanc:8 Useful for video stabilization
fine:box:1,triangle:2 Multi-resolution rendering
fine:sinc*lanc:8,sinc*lanc:8 Multi-resolution rendering
</pre>
<h2>Invariants</h2>
<p>Invariants determine whether the rendered pixel value should be taken from a
single frame, or from an average of all frames. If from a single frame, it can
be the first, last, minimal, or maximal pixel value. Averages include mean
and, in versions 0.8.1 and later, the median. By default, the mean is used.
(Note that using the median value may require allocation of a quantity of
memory linear in the number of frames.) The syntax is as follows:
<blockquote>
<table>
<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
<tr><td>avg:&lt;SSFE&gt;<td><td>Mean value
<tr><td>median:&lt;SSFE&gt;<td><td>Median value [0.8.1 and later]
<tr><td>max:&lt;SSFE&gt;<td><td>Maximum value
<tr><td>min:&lt;SSFE&gt;<td><td>Minimum value
<tr><td>first:&lt;SSFE&gt;<td><td>First value
<tr><td>last:&lt;SSFE&gt;<td><td>Last value
<tr><td>&lt;SSFE&gt;<td><td>Same as avg:&lt;SSFE&gt;
</table>
</blockquote>
<h2>Scaled Sampling Filter with Exclusion (SSFE)</h2>
<p>SSFEs qualify SSFs, indicating whether exclusion regions should be honored.
<blockquote>
<table>
<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
<tr><td>ex:&lt;SSF&gt;<td><td>Honor exclusion regions
<tr><td>nex:&lt;SSF&gt;<td><td>Don't honor exclusion regions
<tr><td>&lt;SSF&gt;<td><td>Same as ex:&lt;SSF&gt;
</table>
</blockquote>
<h2>Scaled Sampling Filter (SSF)</h2>
<p>SSFs indicate whether filtering should occur at the resolution of the output
image, or at the minimum of input and output image resolutions. The former prevents loss
of details; the latter prevents aliasing.
<blockquote>
<table>
<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
<tr><td>fine:&lt;SF&gt;<td><td>Filter at full output image resolution
<tr><td>coarse:&lt;SF&gt;<td><td>Filter at minimum resolution
<tr><td>&lt;SF&gt;<td><td>Same as coarse:&lt;SF&gt;
</table>
</blockquote>
<h3>SSF Options</h3>
<pre>
--afilter &lt;s&gt; Use SSF &lt;s&gt; to interpolate points in alignment.
</pre>
<h2>Sampling Filter (SF)</h2>
<p>SFs are used to limit bandwidth. Primitive functions and pointwise multiplication of these
functions (windowing) are available.
<blockquote>
<table>
<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
<tr><td>sinc<td><td>Sinc filter: (sin &pi;x) / (&pi;x)</td>
<tr><td>lanc:&lt;x&gt;<td><td>Lanczos, diameter x.
<tr><td>triangle:&lt;x&gt;<td><td>Triangle, diameter x.
<tr><td>box:&lt;x&gt;<td><td>Box, diameter x.
<tr><td>zero<td><td>Zero function
<tr><td>&lt;f&gt;*&lt;f&gt;<td><td>Pointwise multiplication (windowing)
</table>
</blockquote>
<h2>Defaults</h2>
<p>ALE defaults are as follows:</p>
<pre>
dchain Varies by <a href="../../defaults/">default setting</a>
achain Varies by <a href="../../defaults/">default setting</a>
afilter internal (approximates triangle:2)
</pre>
<br>
<hr>
<i>Copyright 2003, 2004 <a href="mailto:dhilvert@auricle.dyndns.org">David Hilvert</a></i>
<p>Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
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